Okay.. I checked WHEELWEIGHTS.NET
and the closest analog I found to the newer Nissan Altima rims was the 98-01 rims (16X6) and they are 18 pounds.
16x7 rims go between 11 pounds for forged (Racing Hart CP-035R
though IDK if they sell in bolt pattern/offset for Altima), and 25 pounds. I would figure on something in the ballpark between 20-23 pounds to be safe.
You might also consider lowering your tire profile, though that will be difficult, admittedly. As the overall diameter of the tire/rim decrease you will also increase the amount of force you'll apply to the road through the tire. To do this, you'll need to calculate your current tires'
diameter against the ones you'd like, and that way you'll see the lower diameter and the multiplication of force. The calculator I linked is java based and its used to check to see how much your speedometer will be out, but you can see the difference in tire sizes.
My final thought: if you're looking to maximize your overall speed, holeshot, and agility, consider getting stickier tires (R-compound) as well. You're increasing efficiency everywhere the power is sent to the road, so you want to also increase the ability to transmit the power to the pavement.
Best of luck!